The present invention relates to the lubricating of glass molds in the machine manufacture of glass articles and, more particularly, to a novel lubricant and method and apparatus by which this lubricant is applied to such molds.
In operation of machines in the manufacture of glass articles, such as bottles, containers and the like, molten glass is supplied in gobs or charges from a furnace or hearth at temperatures of about 1800.degree.-2200.degree. F. to a gob chute for conveyance to a split cavity glass forming mold maintained at a temperature of the order of 1000.degree. F. The mold defines a forming cavity that is disposed with its axis generally vertical, and an access opening in one end of the mold permits loading of the gob into the cavity. In one technique, the mold, upon receipt of the molten glass charge, may be inverted and compressed air blown into it to spread the glass into the shape of the cavity and thereby shape the article. The halves of the mold are then separated and the formed article is removed while still hot.
In another type of molding operation, a parison is formed in one mold, which is commonly referred to as the blank mold. This parison may include a neck cavity formed by a neck ring placed adjacent the blank mold to form the neck of the article. After forming the parison by either the above air pressure method or by use of the positive pressing force of a plunger inserted into the mold cavity in the "press and blow" process, the parison is transferred to another mold called the blow mold and formed to a final shape by a blowing technique. In both types of operation, lubricant is either sprayed onto the empty mold cavity by mechaincal means or, alternatively, applied by hand swabbing, which is by far the most prevalent lubricating method today. Such lubrication of the various parts of the mold, including the neck ring, the bottom plate, the mold cavity and the plunger used in the press and blow process, is necessary to improve gob loading and to improve the release of the formed glass products from the mold and thereby prevent flaws in the product caused by sticking.
A typical molding operation involving hand swabbing may be accomplished at the operator's discretion or on a predetermined schedule which requires the machine operator to swab each mold every quarter or half hour, depending upon the type of job. In either prescheduled or discretionary swabbing, the interior parts of the mold will be manually swabbed with a cotton swab which has been dipped into a lubricant. Many different mold lubricants or "dopes" have been applied to various parts of the mold assmebly that contact the glass by either the hand method or by periodically bringing a mechanical spray unit to the proximity of these parts on the machine.
There are several significant disadvantages in present methods of lubricating molds, either by hand or automatically. Hand swabbing, aside from being hazardous, requires application of lubricant at a time when the cycle of the machine mechansim permits. This is usually well in advance of the time the lubricant is most needed and is often a hit-and-miss application. Hand application usually results in intentional over-application of the dope to assure coverage and cut down on the frequency of swabbing, but this results in "dirty" products due to the excess lubricant and also creates a severe smoke hazard in the work area. While the articles rejected because of excess lubricant can be recycled or remelted, considerable expense is involved in the time and wasted energy required to accomplish this.
Mechanized spray units, on the other hand, complicate the cycle of the machine and require that the mold parts to be lubricated be made accessible for insertion of a spray nozzle and time allowed for spraying and removal of the nozzle before beginning the forming cycle again. The extra moving parts create a hazard of interference between the nozzle and the mold parts and also a problem of extra maintenance for the increased number of mechanical parts. Fixed lubricant sprays have been used where spray equipment is stationary, but in these devices uniformity of lubricant application in the areas where it is most needed has not been obtained with regularity.
In either the hand or mechanized method of lubrication, one or more cyles of molding may be missed because of the time required for the swabbing or spraying operation. This ultimately adds to the loss of productivity and may result in non-uniform, excessive or incomplete lubrication of the mold parts.
Further problems are created by the lubricants themselves. Present lubricants normally consist of oils or compounds containing or carrying oils. Such lubricants are unable to withstand the high temperatures and mechanical abrasions of the gob and finished product in the molding operation in a satisfactory manner. These lubricants, when subjected to such temperatures, tend to burn on the surfaces of the mold, or other parts of the molding machine where they may be accidentally dripped, presenting not only a potential fire hazard out invariably creating clouds of smoke, which have been recognized by various states as an actual pollution and health hazard. Finally, in spraying such oils, complete coverage of essential mold parts, such as the neck ring or the bottom plate, is often impossible to obtain unless special and complicated nozzles are used to spray laterally or in an upward direction directly at these parts.